Bike won't start - help!

[K2-K6]

You could try getting a positive feed direct from the battery to the coils to cut out any loom\kill switch variables and see if you get anywhere. Make sure you can break the connection to cut the motor in case of emergency.

If you've got a timing strobe that takes a pulse from ht leads, it will confirm if you are generating sparks.

Assuming if you check and set the timing you are seeing electrical switching across each contact.

[Chris400F]

I was think it sounds like possibly you have a weak spark so maybe not sparking under compression.
Ruling out as many sources of a poor connection as possible sounds a good plan.

[JustcallmeMrT]

Sounds like a plan - I can hook up battery to coils via an alligator clip that I can pull if all goes awry and see if it's something in the loom.

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[Woodside]

Hi are they new ngk plugs.....I had a set in my blade it wouldn't fire at all..
Plugs out looked like a spark but was abit wayward not a nice solid jump across gap....I had flooded it previously. ...asked my mate who is a bike mechanic he said ngk a pretty much fubar'd after a flooding and are good for nothing....He was right new plugs it was good as gold again

[deltarider]

after a blissful week of riding, my bike no longer starts,

Short rides only?

I have done the following:
-checked valve clearances
-checked static timing
-cleaned and gapped the points

Correct order would be:
-cleaned and gapped the points
-checked static timing
(Gapping the points will change the timing.)

-replaced condensers and spark plugs - spark seems ok

What does 'seems ok' mean?
BTW, after replacing condensors it's always wise to check if the connectors are not too close to the plates and as a result are touching them on and of and so making ground intermittently.
After checks, do start attempt with fresh plugs, charged battery and known good plugcaps.

[JustcallmeMrT]

after a blissful week of riding, my bike no longer starts,

Short rides only?

40 minutes to and from work

I have done the following:
-checked valve clearances
-checked static timing
-cleaned and gapped the points

Correct order would be:
-cleaned and gapped the points
-checked static timing
(Gapping the points will change the timing.)

Gapped the points before doing the timing - didn't list them chronologically.

-replaced condensers and spark plugs - spark seems ok
What does 'seems ok' mean?

I put the spark plug up against an engine bolt and observed the spark - I have no quantitative measurement here, so I see a spark, and that's all I can say.  Sometimes it seems a bit spindley,  but how can I quantify it?

[/quote] BTW, after replacing condensors it's always wise to check if the connectors are not too close to the plates and as a result are touching them on and of and so making ground intermittently. [/quote]

I did notice this, so adjusted accordingly.

[/quote] After checks, do start attempt with fresh plugs, charged battery and known good plugcaps.
[/quote]

How can I verify plug caps are good?  my HT leads are new, but I had to cut them to size and wire in the caps myself, which I haven't done before. I followed the directions supplied,  and they did work for a week.... ?


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[Johnwebley]

plug caps do fail over a time,

 check the resistance,

  most resister caps are 5K ohms,but can increase to over 10K as they start to fail



  another item to test,you can also check the HT circuit,by using the probes on each set of plug leads,

 check 1-4 together,and 2-3 together,

 can't remember the actual value when I did mine,but both were the same,and about 44K

 

[deltarider]

In generaly coils secundary circuit will measure 14-15KΩ without caps. Each cap is 5-10KΩ, so with both caps attached the total will be 35KΩ max! 44KΩ doesn't sound right. I'd prefer 5KΩ over 10KΩ caps as resistance increases over time so with 10KΩ caps you'll have no margin left. I wouldn't like mine to be over 8KΩ anyway. At the moment I run zero Ω silicon plugcaps in combination with R(esistor) sparkplugs (usually around 5KΩ). I don't say this is your problem. My summary here is for the record.

[K2-K6]

The ignition is split essentially into two discreet parts with only a common supply but separate from then onwards, although possible, it would be unusual for the mirrored components to fail at identical times and give a dead stop hence my post to arrange a known supply from the battery. You'd expect maybe to drop two cylinders generally if points or coil and maybe one cylinder if plug cap.

Just a very wild stab in the dark, many years ago a friend got me to look at his 250 Yamaha which he'd driven home but it then would not start, I didn't get it to go and everything checked out so we were at a loss as to the problem, somebody else suggested to change the fuel and it went. The reason was really odd though, he'd topped up the tank on the way home in readiness for use of work commuting but he'd put something like 3ltrs of diesel in it as the tank was quite full anyway, it started when hot but there was no way it would fire when cold.

He had a receipt that confirmed the diesel was what he bought when we checked.

[JustcallmeMrT]

The caps I have came with the Dyna coils and HT leads I bought - they're just clips on the end of the leads, with a silicon boot that slides over top, no resistor or anything that I can see.  Is this an issue?

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[deltarider]

The caps I have came with the Dyna coils and HT leads I bought - they're just clips on the end of the leads, with a silicon boot that slides over top, no resistor or anything that I can see.  Is this an issue?

Read the instructions your Dyna coils (what colour?) and HT leads came with and when in doubt contact Dyna. Silicon boots are fine (I run them myself (yellow leads and red boots)), but if there's no resistor in boots and leads (easy to measure) my advice would be to run (R)esistor plugs only. Without any resistor anywhere I don't know if coils will live long. Here's my experience. I bought the green 3 Ω Dyna coils decades ago. First I ran them without any resistors (nor in boots nor in plugs). One coil died after 30.000 kms and I decided it maybe was a better idea to run (R)esistor plugs. But first see what Dyna instructs. I'm not saying this is the cause of your problem, but it wouldn't harm to have this sorted out once and for all.

[JustcallmeMrT]

The caps I have came with the Dyna coils and HT leads I bought - they're just clips on the end of the leads, with a silicon boot that slides over top, no resistor or anything that I can see.  Is this an issue?

Read the instructions your Dyna coils (what colour?) and HT leads came with and when in doubt contact Dyna. Silicon boots are fine (I run them myself (yellow leads and red boots)), but if there's no resistor in boots and leads (easy to measure) my advice would be to run (R)esistor plugs only. Without any resistor anywhere I don't know if coils will live long. Here's my experience. I bought the green 3 Ω Dyna coils decades ago. First I ran them without any resistors (nor in boots nor in plugs). One coil died after 30.000 kms and I decided it maybe was a better idea to run (R)esistor plugs. But first see what Dyna instructs. I'm not saying this is the cause of your problem, but it wouldn't harm to have this sorted out once and for all.

Called up Dyna today and they recommend running their leads without resistor plugs.  They did say that a common issue that results in the same kind of symptoms as my bike is having is lower voltage to the coils due to loom issues, so defo gotta try running a direct feed to the coils.

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[paul G]

Here you go Mr T if you need a relay and socket I have some spare !

[JustcallmeMrT]

No improvement running power direct to the coils from the battery, but I was using small jumper cables with croc clips from Maplins - could the cable be impeding flow too much?  Do they need large diameter cables?

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[deltarider]

Hold it. If your coils happen to be the (green?) 3 Ω coils like mine the last thing you need is a relay. This whole relay hype crossed the Atlantic I'm afraid and I doubt there will be any advantages to speak of.